The following strains were measured using a 0-45-90 degree rosette, with the 0 degree strain gauge aligned with the x-axis direction: €0 = 300 × 10-6, €45 -500 × 10-6 -200 × 10-6. What is the value and €90 of the shear strain Yxy?

It's saying this is not correct. Thank you for your help.

It is still saying that is not correct. I have tried this practice problem over and over and that is the only part that it keeps saying is incorrect. the negative and units are correct. I appreciate your help.

Choose one ball which you think will be most like a perfect machine.  (Explain and rationalize your choice: What is a perfect machine? Can they exist?)